The Adaptation Of Pulmonary O2 Uptake, Limb Blood Flow, And Muscle Deoxygenation During The Off-transient Of Moderate-intensity Exercise

The early time course of adaptation of pulmonary O2 uptake (V̇o2p) (reflecting muscle O2 consumption) and muscle deoxygenation kinetics (reflecting the rate of O2 extraction) were examined during high-intensity interval (HIT) and lower-intensity continuous endurance (END) training. Twelve male volunteers underwent eight sessions of either HIT (8–12 × 1-min intervals at 120% maximal O2 uptake separated by 1 min of rest) or END (90–120 min at 65% maximal O2 uptake). Subjects completed step transitions to a moderate-intensity work rate (∼90% estimated lactate threshold) on five occasions throughout training, and ramp incremental and constant-load performance tests were conducted at pre-, mid-, and posttraining periods. V̇o2p was measured breath-by-breath by mass spectrometry and volume turbine. Deoxygenation (change in deoxygenated hemoglobin concentration; Δ[HHb]) of the vastus lateralis muscle was monitored by near-infrared spectroscopy. The fundamental phase II time constants for V̇o2p (τV̇o2) and deoxygenation kinetics {effective time constant, τ′ = (time delay + τ), Δ[HHb]} during moderate-intensity exercise were estimated using nonlinear least-squares regression techniques. The τV̇o2 was reduced by ∼20% ( P < 0.05) after only two training sessions and by ∼40% ( P < 0.05) after eight training sessions (i.e., posttraining), with no differences between HIT and END. The τ′Δ[HHb] (∼20 s) did not change over the course of eight training sessions. These data suggest that faster activation of muscle O2 utilization is an early adaptive response to both HIT and lower-intensity END training. That Δ[HHb] kinetics (a measure of fractional O2 extraction) did not change despite faster V̇o2p kinetics suggests that faster kinetics of muscle O2 utilization were accompanied by adaptations in local muscle (microvascular) blood flow and O2 delivery, resulting in a similar “matching” of blood flow to O2 utilization. Thus faster kinetics of V̇o2p during the transition to moderate-intensity exercise occurs after only 2 days HIT and END training and without changes to muscle deoxygenation kinetics, suggesting concurrent adaptations to microvascular perfusion.

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Kinetics of O2 uptake, leg blood flow, and muscle deoxygenation are slowed in the upper compared with lower region of the moderate-intensity exercise domain

Journal of Applied Physiology ◽

10.1152/japplphysiol.01183.2004 ◽

2005 ◽

Vol 99 (5) ◽

pp. 1822-1834 ◽

Cited By ~ 64

Author(s):

Shelley L. MacPhee ◽

J. Kevin Shoemaker ◽

Donald H. Paterson ◽

John M. Kowalchuk

Keyword(s):

Blood Flow ◽

Knee Extension ◽

Single Step ◽

Moderate Intensity ◽

Moderate Intensity Exercise ◽

Leg Blood Flow ◽

Muscle Deoxygenation ◽

Knee Extension Exercise ◽

Kinetics Of ◽

Male Subjects

Six male subjects [23 yr (SD 4)] performed repetitions (6–8) of two-legged, moderate-intensity, knee-extension exercise during two separate protocols that included step transitions from 3 W to 90% estimated lactate threshold (θL) performed as a single step (S3) and in two equal steps (S1, 3 W to ∼45% θL; S2, ∼45% θL to ∼90% θL). The time constants (τ) of pulmonary oxygen uptake (V̇o2), leg blood flow (LBF), heart rate (HR), and muscle deoxygenation (HHb) were greater ( P < 0.05) in S2 (τV̇o2, ∼52 s; τLBF, ∼ 39 s; τHR, ∼42 s; τHHb, ∼33 s) compared with S1 (τV̇o2, ∼24 s; τLBF, ∼21 s; τHR, ∼21 s; τHHb, ∼16 s), while the delay before an increase in HHb was reduced ( P < 0.05) in S2 (∼14 s) compared with S1 (∼20 s). The V̇o2 and HHb amplitudes were greater ( P < 0.05) in S2 compared with S1, whereas the LBF amplitude was similar in S2 and S1. Thus the slowed V̇o2 response in S2 compared with S1 is consistent with a mechanism whereby V̇o2 kinetics is limited, in part, by a slowed adaptation of blood flow and/or O2 transport when exercise was initiated from a baseline of moderate-intensity exercise.

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Hippocampal Blood Flow Is Increased After 20 min of Moderate-Intensity Exercise

Cerebral Cortex ◽

10.1093/cercor/bhz104 ◽

2019 ◽

Vol 30 (2) ◽

pp. 525-533 ◽

Cited By ~ 4

Author(s):

J J Steventon ◽

C Foster ◽

H Furby ◽

D Helme ◽

R G Wise ◽

...

Keyword(s):

Blood Flow ◽

Temporal Dynamics ◽

Therapeutic Potential ◽

Cerebrovascular Reactivity ◽

Moderate Intensity ◽

Moderate Intensity Exercise ◽

Exercise Interventions ◽

Before And After ◽

Exercise Induced

Abstract Long-term exercise interventions have been shown to be a potent trigger for both neurogenesis and vascular plasticity. However, little is known about the underlying temporal dynamics and specifically when exercise-induced vascular adaptations first occur, which is vital for therapeutic applications. In this study, we investigated whether a single session of moderate-intensity exercise was sufficient to induce changes in the cerebral vasculature. We employed arterial spin labeling magnetic resonance imaging to measure global and regional cerebral blood flow (CBF) before and after 20 min of cycling. The blood vessels’ ability to dilate, measured by cerebrovascular reactivity (CVR) to CO2 inhalation, was measured at baseline and 25-min postexercise. Our data showed that CBF was selectively increased by 10–12% in the hippocampus 15, 40, and 60 min after exercise cessation, whereas CVR to CO2 was unchanged in all regions. The absence of a corresponding change in hippocampal CVR suggests that the immediate and transient hippocampal adaptations observed after exercise are not driven by a mechanical vascular change and more likely represents an adaptive metabolic change, providing a framework for exploring the therapeutic potential of exercise-induced plasticity (neural, vascular, or both) in clinical and aged populations.

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Dynamics of middle cerebral artery blood flow velocity during moderate-intensity exercise

Journal of Applied Physiology ◽

10.1152/japplphysiol.00995.2016 ◽

2017 ◽

Vol 122 (5) ◽

pp. 1125-1133 ◽

Cited By ~ 13

Author(s):

Sandra A. Billinger ◽

Jesse C. Craig ◽

Sarah J. Kwapiszeski ◽

Jason-Flor V. Sisante ◽

Eric D. Vidoni ◽

...

Keyword(s):

Blood Flow ◽

Steady State ◽

Dynamic Response ◽

Moderate Intensity ◽

Artery Blood Flow ◽

Moderate Intensity Exercise ◽

Cerebrovascular Function ◽

Exercise Response ◽

Response Profile ◽

Health And Disease

The dynamic response to a stimulus such as exercise can reveal valuable insights into systems control in health and disease that are not evident from the steady-state perturbation. However, the dynamic response profile and kinetics of cerebrovascular function have not been determined to date. We tested the hypotheses that bilateral middle cerebral artery blood flow mean velocity (MCAV) increases exponentially following the onset of moderate-intensity exercise in 10 healthy young subjects. The MCAV response profiles were well fit to a delay (TD) + exponential (time constant, τ) model with substantial agreement for baseline [left (L): 69, right (R): 64 cm/s, coefficient of variation (CV) 11%], response amplitude (L: 16, R: 13 cm/s, CV 23%), TD (L: 54, R: 52 s, CV 9%), τ (L: 30, R: 30 s, CV 22%), and mean response time (MRT) (L: 83, R: 82 s, CV 8%) between left and right MCAV as supported by the high correlations (e.g., MRT r = 0.82, P < 0.05) and low CVs. Test-retest reliability was high with CVs for the baseline, amplitude, and MRT of 3, 14, and 12%, respectively. These responses contrasted markedly with those of three healthy older subjects in whom the MCAV baseline and exercise response amplitude were far lower and the kinetics slowed. A single older stroke patient showed baseline ipsilateral MCAV that was lower still and devoid of any exercise response whatsoever. We conclude that kinetics analysis of MCAV during exercise has significant potential to unveil novel aspects of cerebrovascular function in health and disease. NEW & NOTEWORTHY Resolution of the dynamic stimulus-response profile provides a greater understanding of the underlying the physiological control processes than steady-state measurements alone. We report a novel method of measuring cerebrovascular blood velocity (MCAv) kinetics under ecologically valid conditions from rest to moderate-intensity exercise. This technique reveals that brain blood flow increases exponentially following the onset of exercise with 1) a strong bilateral coherence in young healthy individuals, and 2) a potential for unique age- and disease-specific profiles.

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